jsDef
A tool to parse your comment in Javascript to generate documentation in a simpler or/and straight-forward way.
Why this
To answer this question, we need to answer two sub-questions: "Why bother writing comments and docs?" and "Why not using alternative solution?"
Why bother
Javascript is a weakly-typed language. Having that said, types (or data structures) indeed exist in every places in your project. For instance, dealing with data fetched from the backend, you can do nothing, before you know the actual "output" of the REST api.
Types serves as the "contract" between you and other developers, or in an even fancy way, "contract" between "You" from different time (i.e, past, present and future you).
Having types documented can greatly benefit a lot as you will spend less time guessing, and/or finding clue of how a data is constructed. In the real world, we witness someone invoke an actual xhr so that he/she can get some idea of what an REST api returns, and that happens frequently enough that holds us back in development.
Why not alternatives
TypeScript
TypeScript is believed by quite some people now that it will be the future of Javascript. And it's kinda true, considering the benefit it provides to us!
However, adopting TypeScript might not suit some situations. Taking into account the history code debt, the current team's tech stack, etc. So it might not be a solution in some circumstances.
By the way, TypeScript is really worth trying if you have not.
JsDoc